Synthesis of a number of bacterial proteins including glutamine synthetase, amino acid transport components and degradative enzymes, and nitrogenase is increased under nitrogen limiting conditions. In enteric bacteria increased synthesis appears to be mediated by products of nitrogen regulatory genes ntrA, ntrB, and ntrC, which activate transcription. Our major goals are to determine functions of the individual ntr products in regulating transcription and to identify sites to which they bind within the promoter-operator for glnA, the structural gene encoding glutamine synthetase. We will attempt to demonstrate regulatory effects of ntr products on glnA expression in vitro.